Delayed Release Delivery Systems And Methods

ABSTRACT

A delayed release delivery system comprises a hydrophilic core particle having surface pores and containing a liquid. The particle is encapsulated in a polymer having a hydrophobic backbone and hydrophilic pendant groups. At least some of the surface pores adjacent the hydrophilic pendant groups are blocked in the presence of water and unblocked in the absence of water. The treated particle contains liquid in a weight ratio of the liquid to the porous core particle of at least 400:1.

FIELD OF THE INVENTION

The present invention relates to particles which can act as a sustaineddelivery system for fragrance or skin, scalp and hair benefitingredients, methods for preparing the particles, and compositionscontaining the particles. More specifically, the particles absorbfragrance or actives and release the fragrance or actives gradually overan extended period of time.

BACKGROUND OF THE INVENTION

Fragrance is used in a variety of products to enhance the consumer'sdelight in using those products. The desirability of producing productswhich retain their scent for an extended period of time afterapplication to skin, scalp or hair, has long been recognized. Despitemany efforts in this direction, most commercial products for skin, scalpand hair have an intense, pleasant odor initially but, disappointingly,tend to lose their scents within minutes after being applied. Attemptsmade to solve the problem include using inorganic carriers impregnatedwith fragrance for incorporation into products. EP 0 332 259A disclosesperfume particles made by adsorbing perfume onto silica. U.S. Pat. No.5,336,665 discloses free-flowing hydrophobic porous inorganichydrophobic carrier particles, such as aluminosilicates, having acertain pore volume and pore diameter and having perfume adsorbed intothe particles. A fragrant material composed of aggregates of sodiumchloride granules and having a fragrant oil absorbed in the poresbetween granules is disclosed in U.S. Pat. No. 5,246,919.

Efforts have been made to increase the amount of time that fragrancesremain on keratinous surfaces of the body without increasing fragranceload, such as by the use of coatings and microencapsulation systems. Afragrant bead composition made up of a multiplicity of prilled ureabeads having an adherent surface coating containing a fragrance isdescribed in U.S. Pat. No. 4,020,156. A discontinuous surface coatingfor particles which permits a controlled release of actives from anunderlying deposit on a core particle is described in U.S. 2006/0153889.

Microencapsulation technology is well known in the art and is generallydirected to encapsulating core materials that require protection untiltime of use in a protective covering. Generally, a high viscosity fluidwill be dispersed more slowly from a carrier which tends to extendfragrance duration, while a lower viscosity fluid will enhance theintensity of the scent by virtue of a higher evaporation rate. Timerelease microcapsules release their core materials at a controlled rate.The result is that the encapsulated material has a longer effective lifesince it is not immediately released from the protective microcapsule. Apolymeric encapsulated liquid fragrance which is further treated with acationic polymer to improve deposition is described in U.S. Pat. No.7,294,612. A pre-glass agglomeration of fused microspheres usesmicrocapillary action to quickly uptake oil-based or alcohol-basedliquids to more than double the weight of the pre-glass agglomeration,as described in U.S. Pat. No. 6,245,733. A cosmetic materialencapsulated by a frangible capsule of thermo-softening material that issolid at room temperature but which will rupture when the composition isrubbed on a skin surface and melts up on application to the skin isdescribed in U.S. Pat. No. 7,622,132.

Notwithstanding the above, there is still an ongoing need for fragrancedproducts which demonstrate an extended duration of continuous release offragrance to the skin, scalp and hair, over extended periods of time.

SUMMARY OF THE INVENTION

According to one aspect of the invention, a delayed release deliverysystem comprising at least one treated particle is provided.

In one embodiment of this aspect of the invention, the treated particlecomprises a hydrophilic core particle having surface pores and a liquidcontained therein. The hydrophilic core particle is further encapsulatedby a polymer having a hydrophobic backbone and a plurality ofhydrophilic pendant groups. At least some of the surface pores adjacentthe hydrophilic pendant groups are blocked in the presence of water andunblocked in the absence of water.

In a further embodiment of this aspect of the invention, the treatedparticle comprises a porous core particle having a porous surface, and aliquid absorbed therein. The weight ratio of the liquid to the porouscore particle is at least about 400:1, such as from about 400:1 to about800:1.

In accordance with a further aspect of the invention, a method forpreparing a delayed release delivery system is provided.

In one embodiment of this aspect of the invention, the method forpreparing a delayed release delivery system includes the steps of:

(a) providing at least one hydrophilic core particle having surfacepores and having a liquid absorbed therein;

(b) contacting the particle of (a) with a liquid polymer for a timesufficient to encapsulate the at least one particle with the liquidpolymer to form at least one treated particle, wherein the liquidpolymer has a hydrophobic backbone and a plurality of hydrophilic sidechains, and wherein at least some of the surface pores on thehydrophilic core particle adjacent the hydrophilic side chains areblocked in the presence of water and unblocked in the absence of water;and

(c) dispersing the at least one treated particle in anaqueous-containing cosmetically acceptable vehicle.

In accordance with a further embodiment of this aspect of the invention,the method for preparing a delayed release delivery system comprises thesteps of:

(a) providing a porous core particle; and

(b) contacting the porous core particle with a liquid under conditionssufficient for the liquid to be absorbed into the core particle in theweight ratio of the liquid to the porous core particle of at least about400:1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Delayed release delivery systems of the invention comprise a porousparticle having a liquid absorbed therein.

A delayed release delivery system comprises at least one treatedparticle comprising a hydrophilic core particle having surface poreswhich is encapsulated with a polymer. The polymer has a hydrophobicbackbone and a plurality of hydrophilic pendant groups. The polymerblocks pores on the surface of the treated particle with the exceptionthat at least some pores on the particle surface which are situatedadjacent the hydrophilic pendant groups on the polymer are blocked inthe presence of water and unblocked in the absence of water. In thepresence of an aqueous-containing environment, a liquid contained withinthe treated particle is retained in the particle, since water moleculesare attracted to the hydrophilic pendant groups and block at least someof the surface pores adjacent the pendant groups.

The treated particles maintain integrity when suspended in anaqueous-containing base during storage, or in an aqueous-containingproduct. Upon being rubbed into skin, for example, as the water in theproduct evaporates, the water molecules blocking pores adjacent thehydrophilic pendant groups on the polymer pull away from the porespermitting a liquid contained in the treated particle to be graduallyreleased through the pores in a slow and sustained manner.

Any hydrophilic porous core particle capable of absorbing liquid may beused in preparing the delayed release delivery system. Typically, suchparticles are formed of an inorganic material, including, but notlimited to silica, silica silylate, and calcium silicate. Microspheresformed of these inorganic materials, and particularly, hydrophilicmicrospheres, are preferred for use in the delayed release deliverysystems of the invention. Hydrophilic microspheres useful in theinvention may be natural or synthetic and have an average particle sizeof from about 100 nm to about 50 Microspheres having a high affinity foroil absorption are particularly preferred. One such microsphere isformed of calcium silicate, available as Florite® from TomitaPharmaceutical Co., Ltd., having a particle size of about 29 μM. Thissynthetic material has a petaloid crystal structure with notably deep,large pore size and volume, and excellent liquid absorbency. Incomparison with other inorganic materials, this calcium silicate absorbsoil and water of at least five times its weight. 650 g of oil areabsorbed by 100 g of this calcium silicate powder. Microspheres formedfrom silica, such as Silica shells Jr. are also useful. Thesemicrospheres, available from KOBO, have a particle size of about 3 μM,and absorb 400-600 g of oil per 100 g of silica powder. Also useful aremicrospheres formed of silica silylate, a fumed silica, available asCAB-O-SIL TS-530 from Cabot. The silica is treated withhexamethyldisilazane. The treatment replaces many of the surfacehydroxyl groups with trimethylsilyl groups rendering the silicaextremely hydrophobic

Polymers useful in the delayed delivery systems of the present inventionhave a hydrophobic backbone and pendant hydrophilic groups or sidechains. The backbone of the polymer is sufficiently hydrophobic toadhere well to the surface of the liquid-filled porous particle. Thehydrophilic side chains behave like the bristles of a brush. They aresufficiently long and suitably spaced along the polymer backbone toenable the side chains to not only attract water but to trap and holdit. Particularly preferred polymers are those having a siliconebackbone. Silicone adheres well to the porous particles and may bemodified by the addition of hydrophilic side chains. One such preferredpolymer has a silicone backbone with polyglycerol side chains. Thesilicone backbone or hydrophobic side of the polymer adheres to theporous particle surface, anchoring in the pores. This polymer adheresparticularly well to hydrophilic porous particles filled with anoil-containing liquid. Oil in the pores makes the hydrophilic particlebehave like a hydrophobic particle so as to enable the polymer to adherewell to the particle surface. The polyglycerol side chains form thehydrophilic side of the polymer and do not attach to the microspheresurface. When polymer-coated treated particles of the invention aredispersed in an aqueous-containing base, water molecules in the base areattracted to the side chains. The water molecules hydrogen bond to theside chains and surround each particle. The water molecules plug thespaces in the polymer at the points where the side chains extend fromthe polymer backbone. The greater the number of the side chains, themore water is associated with the treated particles. When anaqueous-containing product containing the treated particles is rubbedinto skin, water evaporates from the product containing the treatedparticles. The water associated with the treated particles is the lastto evaporate. Once those water molecules are no longer available to plugthe holes in the silicone backbone (where the side chains are located),the previously plugged pores in those areas are exposed, and fragrancebegins to exit the treated particle.

Ambient humidity levels can affect evaporation of water from the productcontaining the liquid-filled treated particles. The higher the ambienthumidity, the slower the release of liquid due to slower evaporation ofwater.

The more liquid entrapped in the treated particles, the longer it willtake for the liquid, for example, a fragrance oil-containing liquid, tobe released and the longer the duration of the scent on the skin. Thediffusivity of the liquid will also affect the release time.

Suspending the treated particles in a non-compatible vehicle can furtherretard the release of the liquid entrapped in the particle pores. Forexample, a treated particle containing a fragrance oil may be dispersedin an aqueous base for storage, or in an aqueous-containing product.

Another factor which would be expected to impact controlled release ofthe liquid, for example a fragrance oil, and therefore the endurance offragrance on the skin, includes the thickness of the polymer coating onthe porous particles. As the polymer coating is hydrophobic, once waterhas evaporated from a skin product, oil on the skin will slowly dissolvethe coating on the treated particles, permitting the liquid to escape.As polymer thickness increases, the longer will be the duration of therelease of the entrapped liquid.

Similarly, the amount of the oil phase in a product in which the treatedparticles are incorporated will also have an effect on the timed releaseof contained liquid. Once water has evaporated from the product, the oilin the product will begin to gradually dissolve the hydrophobic polymercoating and lead to the sustained release of the liquid from theparticles. The lesser the amount of the oil phase in the product, theslower the release of the liquid.

The amount of liquid-containing treated particles in a productcontaining the particles will also impact the duration of fragrance onthe skin to which the product is applied.

Any liquid capable of being absorbed into the hydrophilic core particlesmay be used in preparing the delayed release delivery system. The liquidmay be aqueous-based, oil-based, an oil-in-water emulsion, asilicone-in-water emulsion, a water-in-oil emulsion, a water-in-siliconeemulsion, or a multiple emulsion. Preferably, the liquid will beselected from those containing a fragrance oil, a skin, scalp or hairbenefit active, and combinations thereof.

The delayed release delivery system may be prepared by the followingsteps:

(a) providing at least one hydrophilic core particle having surfacepores and a liquid absorbed therein;

(b) contacting the particle of (a) with a liquid polymer underconditions sufficient to encapsulate the at least one particle with theliquid polymer to form at least one treated particle, wherein the liquidpolymer has a hydrophobic backbone and a plurality of hydrophilic sidechains, and wherein at least some of the surface pores on thehydrophilic core particle adjacent the hydrophilic side chains areblocked in the presence of water and unblocked in the absence of water;and

(c) dispersing the at least one treated particle in anaqueous-containing cosmetically acceptable vehicle.

The hydrophilic core particle may be any hydrophilic porous particlecapable of absorbing liquid therein, as discussed hereinabove.

Any liquid capable of being absorbed into the hydrophilic core particlesmay be used in preparing the delayed release delivery system, asdiscussed hereinabove. The liquid may be absorbed into the at least onehydrophilic core particle by any suitable method known in the art.

The step of contacting the liquid-filled treated particle with thepolymer may be carried out using any suitable method known to thoseskilled in the art for applying a coating to a particle, including, butnot limited to, at least one of mixing, spray coating, and sonication.

A preferred method of encapsulating the liquid-filled core particleswith the polymer is by the use of sonication. The average size of theliquid-filled particles (e.g., 3 μm silica particles filled with afragrance oil-containing liquid) is measured by Transmission ElectronicMicroscopy (TEM). 70% water, 28% liquid-filled particles and 2% liquidpolymer are mixed in a vessel to form a slurry. The slurry is thensonicated for 30 minutes with medium intensity, 20 kHz, at 25° C. usingan ultrasonic probe such as available from Sonicor Instrument Co., toresult in a thick colloidal suspension. The suspension is centrifugedfor 15 minutes at 1000 rpm in order to precipitate the particles andremove unattached polymer material. The resultant mixture is washed withdeionized water, and the washing procedure is repeated three times. TEMis used again after sonication to measure the uniformity and thethickness of the polymer coating on the treated particles. The thicknessof the polymer coating will be that amount which will permit the polymerto anchor to the pores, while avoiding a too thick coating which may beexpected to adversely affect the release of the liquid. The polymerthickness will preferably be in the range of from about 10 nm to about30 nm. A coating of less than about 10 nm would not be expected touniformly coat the porous particle, while a thickness of greater thanabout 30 nm may be expected to essentially prevent the release of theliquid from the treated porous particles. To prevent dehydration of thetreated particles, which would activate the release of the liquid, thetreated particles are then submerged in about 70 weight % water.

Polymers suitable for use in the delayed release delivery system of theinvention include, but are not limited to, any of those discussedhereinabove.

In a further embodiment of the present invention, the delayed deliverysystem comprises at least one treated particle comprising a coreparticle having a porous surface, and a liquid absorbed in the coreparticle. The ratio of the weight of the liquid to the weight of thecore particle being at least about 400:1. More preferably, the ratio isbetween about 400:1 and about 800:1, including any ratio there-between,including 401:1 to 799:1, and any range therein.

Any porous particle capable of absorbing liquid may be used in preparingthe delayed release delivery system, as discussed hereinabove.

The delayed release delivery system may be prepared by the followingsteps:

(a) providing a porous core particle; and

(b) contacting the porous core particle with the liquid under conditionssufficient for the liquid to be absorbed into the porous core particlein the weight ratio of the liquid to the porous core particle of atleast about 400:1.

Porous core particles useful in this method for preparing the delayedrelease delivery system may include any porous particle capable ofabsorbing liquid therein. Useful porous particles may include, but arenot limited to, the hydrophilic particles discussed hereinabove.

The liquid is absorbed into the core particle by contacting the coreparticle with the liquid at a pressure of at least 100 psi for at least30 minutes. More preferably, the pressure used is in the range ofgreater than 100 psi to about 1000 psi, including any valuethere-between, including 101 to 999 psi and any integer within thatrange, such as 300 psi, 500 psi, 700 psi, and so forth, The contactingtime may be any time from about 30 minutes up to about 2 hours, such asfor about 1 hour. The contacting step may be repeated at least once, forexample, one to three times. The high pressure spreads the pores in theparticles enabling the particles to hold more liquid, and also propelsthe liquid into the pores. The pressure and the time needed to achievethe desired amount of liquid absorption increase proportionately withthe density of the liquid. Generally, porous particles and the liquid tobe absorbed are mixed in a ratio of from about 1:5 to about 1:10 ofporous particles to liquid, and the resulting slurry is transferred to ahigh pressure tank. The slurry is then subjected to high pressure for atleast 30 minutes, and up to about 2 hours.

The method may further comprise the step of encapsulating the treatedparticle in a polymer coating as described hereinabove.

The absorption of liquid by the porous core particle (e.g., microsphere)may be facilitated by compatibilizing the surface tension of the liquidwith the surface tension of the porous particle. The surface tension ofthe liquid may be in the range of from about 30-72 dyne/cm. For example,a hydrophobic liquid, such as a liquid containing a fragrance oil, mayhave a surface tension in the range of from about 30-45 dyne/cm.Diluents may be combined to modify the surface tension of the fragranceoil. A porous particle containing a hydrophobic liquid, such as afragrance oil, will typically have a surface tension in the range offrom about 40-70 dyne/cm. The surface tension is modified in certainembodiments in which a polymer having a hydrophobic backbone andhydrophilic side chains or pendant groups is coated onto theliquid-containing porous particle. In that case, the surface tension ofthe coated particle will be in the range of from about 60-72 dyne/cm toensure that the treated particles are dispersible in the water phase ofa product. As discussed above, when water evaporates from theaqueous-containing product, release of the liquid contained in theporous particle will be activated. Surface tension may be measured byany method known in the art for this purpose. An example of aninstrument useful in measuring surface tension of liquids is the ForceTensiometer—K100, available from Krüss.

One method for determining the pressure and time needed for a particularliquid, for example, a liquid containing a fragrance oil, to be absorbedinto the porous particles, uses confocal laser scanning microscopy(CLSM). Samples are prepared by mixing fragrance oil with a fluorescentdye, for example, Nile red, incorporating the dye-containing oil intodiluent, and mixing the liquid with core particles under conditions ofvarying pressure and time. Each prepared sample of the liquid-containingmicrospheres is placed on a micro slide and examined under the confocalmicroscope. Emitted/reflected light is transmitted to electrical signalsby a photomultiplier and displayed on a computer monitor screen. Thismethod permits measurement of the surface area and mathematicalcalculation of the volume occupied by the fragrance oil.

Any liquid capable of being absorbed into the core particles may be usedin preparing the delayed release delivery system, as discussedhereinabove. Liquids, containing fragrance or actives in diluent, to beabsorbed by the core particles, may be hydrophilic or hydrophobic. Asdiscussed hereinabove, for optimal loading of liquid in the porousparticle, the surface tensions of the liquid and the core particleshould be compatible. For example, to modify the surface tension of afragrance oil to be more compatible with the surface tension of the coreparticle the fragrance oil may be combined with one or more diluents.

Fragrances suitable for use in this invention include withoutlimitation, any fragrance of combination of fragrances, includingfragrant oils, plant extracts, synthetic fragrances, or mixturesthereof, which are compatible with and capable of being encapsulated inthe delayed release delivery systems of the invention, and which alsoare compatible with the encapsulation processes employed. Suitablefragrances include but are not limited to those derived from fruits,flowers, and herbs, as well as oils, including essential oils. A sourceof suitable fragrances is found in Poucher's Perfumes Cosmetics andSoaps, Tenth Edition, Hilda Butler, 2000.

Treated particles, whether or not encapsulated in polymer, may besuspended in a cosmetically acceptable vehicle. Such cosmeticallyacceptable vehicle may be aqueous-based, oil-based, an oil-in-wateremulsion, a silicone-in-water emulsion, a water-in-oil emulsion, awater-in-silicone emulsion, or a multiple emulsion. In the case of thetreated particle encapsulated in polymer, the vehicle will beaqueous-containing. The vehicle may comprise a cosmetically furthercosmetically acceptable skin, scalp or hair benefit ingredient.

What is claimed is:
 1. A delayed release delivery system comprising atleast one treated particle, the treated particle comprising a coreparticle having a porous surface, and having a liquid absorbed therein,wherein a ratio of the weight of the liquid to the weight of the coreparticle is at least about 400:1.
 2. The delayed release delivery systemof claim 1, wherein the ratio of the weight of the liquid to the weightof the core particle is between about 400:1 and about 800:1.
 3. Thedelayed release delivery system of claim 1, wherein the liquid isaqueous-based, oil-based, an oil-in-water emulsion, a silicone-in-wateremulsion, a water-in-oil emulsion, a water-in-silicone emulsion, or amultiple emulsion.
 4. The delayed release delivery system of claim 1,wherein the liquid contains a fragrance oil, a skin benefit active, ascalp benefit active, a hair benefit active, or a combination thereof.5. The delayed release delivery system of claim 1, wherein the liquidand the core particle have compatible surface tensions.
 6. The delayedrelease delivery system of claim 1, wherein the core particle is amicrosphere having an average particle size of from about 100 nm toabout 50 μm.
 7. The delayed release delivery system of claim 1, whereinthe treated particle further comprises a polymer coated on the surfacethereof wherein the polymer comprises a hydrophobic backbone andhydrophilic side chains.
 8. A composition comprising the delayed releasedelivery system of claim 1 in a cosmetically acceptable vehicle.
 9. Acomposition comprising the delayed release delivery system of claim 7 ina cosmetically acceptable vehicle.
 10. The composition of claim 8,comprising at least one further skin, scalp or hair benefit ingredient.11. The composition of claim 9, comprising at least one further skin,scalp or hair benefit ingredient.